Parallel rule



July 7, 1959 l. A. MolNTosH 2,893,127

PARALLEL RULE Filed Aug. 2.3, 195s 2 Sheets-Shee 1 2 sheets-'sheet '2 l. A. MlNTosl-ll PARALLEL RULE July 7, 1959 Filed Aug'. 23. -1956 I, .I 17% :tn H

United States Patent O 2,893,127 PARALLEL RULE Ian Arthur McIntosh, Westmead, near Sydney, New South Wales, Australia Application August z3, 1956, serial No. 605,820

Claims priority, application Australia August 25, 1955 I Claims. (Cl. '3S-109) This invention relates to parallel rules of the kind comprising a straight edge incorporating a scale mounted on rollers to facilitate the movement of the rule over a sheet `when plotting a course or position.

As constructed hitherto, such rules have not proved altogether satisfactory. j

In one construction, |a longitudinal roller was incorporated in the underface of the rule to facilitate its movement over a sheet. The movement of this rule was limited to a right angle to its drawing edge and consequently such a4 rule only 4had very limited application and was of nuse'whateve in plotting a course or position -Which was not ata light angle to its drawing edge.

In another construction -twol -sets of rollers were incorporated in the underface of the rule to facilitate its movement over a she'et. Means were provided to move either set of rollers intoy operative position. This rule was capable of movement in two directions butv the multiplicity of partsv engendered slackness which was fatal to accurate work yand` made the'nule completely unsatisfactory Where accurate work was required.

This invention provides a parallel rule which is capable of universal movement in the plane of the table on which it is used and the parts are so constructed and rarranged that movement of the rule due to slackness in the working parts is avoided. This parallel rule can be used to plot direction and distance in one operation.

According to this invention the parallel rule has two pairs of supporting rollers mounted in the bottom, one pair being adjacent each end thereof. The rollers have larcuate tread surfaces and each pair of rollers are rotatably mounted on axles located at a right angle one to the other in a supporting member which is mounted for rotation at a right angle to the axis of rotation of the rollers.

In one embodiment of the invention the parallel rule has a longitudinal cavity therein open yat the bottom and extending between the end walls thereof. A shaft rotatably mounted in the cavity has adjacent each end two slots made diametrically therethrough. One slot of each pair is at `a righ-t angle to the other and the respective slots at one end of the shaft are in true alignment with the corresponding slots at the other end of the shaft. A roller having an arcuate tread surface is 1rotatably mounted in each slot in such manner that there is no play or slackness in the mounting. Each roller projects from its slot and the width of each roller is such that the respective side edges of the tread of each pair of rollers are in alignment.

This arrangement provides that as one roller of each pair moves away from the table due to turning of the shaft the other Iroller of each pair engages the table, consequently the Support of the parallel rule by the rollers is continuous and the rule is capable of universal movement in the plane of the table.

ICC

' the rule showing the arrangement of the shaft and rollers.

Figs. 4 and 5 are sectional elevations on lines 4 4 and 5-5 of Fig. 3 respectively.

Fig. 6 is an inverted plan, similar to Fig. 3 of -a modification of the invention.

Fig. 7 is a central sectional elevation of one end of the rule showing the arrangement of the shaft and rollers according to the modification.

Fig. 8 is a sectional elevation on lines 8 8 of Fig. 7.

Referring to Figs. l to 5, the parallel rule comprises a body 7 having on one side a ledge 8 forming one edge 9 of the rule. A longitudinal cavity 10 is formed in the body 7. It is open at the bottom and extends between the end walls 11 and 12. On the other side of the body 7 there is a ledge 13 which is set downwardly at an acute angle land forms the opposite edge 14 of the rule; this ledge is sufficiently wide enough to accommodate a scale 15 detachably secured thereon by spring clips 16 iixed to the ledge. The side walls of the body are tluted as at 17 to provide a non-slip surface whereby the rule can be gripped by the fingers and manipulated on a sheet when plotting a course.

A tubular shaft 18 is adjustably and rotatably mounted in the longitudinal cavity 10 on pin point journal pins 19 screwed through the end walls 11 'and 12 @and centering in conical bearings 20 formed in end plates 21 xed in the end of the tube 18. The pin point journal pins vare locked in set position by grub screws 22 screwed through the end walls 11 and 12. Two pairs of slots 23-'24 and 2 5-26 are made through the vtube 18 ,adjacent each end. One slot of each pair is located at a right angle to the other and the respective slot-s at one end of the shaft are in true alignment with the slots at the other end of the shaft. That is to say, slot 23 is in alignment with the slot 25 and slot 24 is in alignment vwith the slot 26 (see Fig. 6). A roller 27 having an arcuate tread surface 28 formed on a -true radius as a segment of a circle is rotatably mounted in each of the slots 23-24 and 25--26 in such a manner that there is no play or slackness in the mounting. The major diameter of each roller 27 is greater than the diameter of the shaft 18 and the width of each roller is such that the respective side edges of the tread of each pair of rollers are in alignment.

This arrangement as stated previously provides that as one roller of each pair moves away from the table due to turning of the shaft the other roller of each pair engages the table, consequently the support of the parallel rule by the rollers is continuous.

Each roller 27, having an arcuate tread surface formed on -a true radius as a segment of a sphere is bored axially and intermediate the ends of the bore a V groove 29 is made to form part of a ball race. Cylindrical blocks 30--30a fare mounted in the bore from each end and the edges 31 of the blocks juxtaposed the V groove 29 are shaped as to form the other part of the ball race. The blocks 30-30a lare bored and an axle 32 passing through the blocks is supported in the side walls of the slots as at 33--33a. A pair of adjusting screws 34-35 in the side walls of the slots press the cylindrical blocks 30-30a into firm engagement with ball bearings 36 accommodated n the ball race.

According to the rnodication illustrated in Figs. 6 to 8 the shaft 18 is provided with slots 23-24, 25-26 for the reception of rollers -as before. In this case, however, the bore in the rollers 27 is stepped at each end as at 37 to provide a seat bore. An annular disc 38 is mounted in each end of the bore. Preferably the discs are recessed as at 39 to accommodate a spring washer 40 mounted on the axle 32. The rollers are rotatably mounted on the axles 32 which are supported in the side walls of the slots as stated above. The spring washers take up any slack between the rollers 27 and' the side walls of the slots.

I claim:

l. A parallel rule comprising, an elongated body having a cavity opening at its bottom side and bounded by opposite end walls and lateral side walls terminating in outwardly aring ledges one of which is provided with a scale, a tubular shaft axially mounted for rotation in the end walls, said shaft having adjacent each end a pair of slots extending diametrically therethrough, one slot of each pair being at a' right angle to the other slot and in alignment with the corresponding slot of the other pair, a roller having a spherical tread surface rotatably mounted inl each slot and projecting therefrom in the provision of pairs of rollers the width of the tread ofeach roller of said pairs of rollers being such that the respective side edgesl of pairs of rollers are in alignment, said spherical surfaces of each respective pair of rollers being alternately engageable with a working surface, whereby the said rule may be moved over a surface in 4the direction of the axis of its body or at right angles thereto.

2. A parallel rule having a longitudinal cavity therein defined by top, end and side walls and open at the bottom, an elongated shaft rotatably mounted from said end walls in said cavity, said shaft having adjacent each end a pair of slots made diametrically therethrough, one slot of each pair being at a right angle to the other slot and in alignment with the corresponding slot of the other pair, a roller having a spherical tread surface, said roller being rotatably mounted in each slot on an axle and'said tread surface projecting` from the slot and below the free edges of the respective walls defining said cavity, the width of each roller being such that the respective side edges of pairs of rollers which are on an axle inthe same angular direction are in alignment, said spherical surfaces of each respective pair of rollers alternately engaging a working surface on which the rule is supported as said elongated shaft is turned.

3. A parallel rule according to claim 2 having the shaft mounted on pin point journal pins adjustably mounted in end walls of the cavity and lock means adapted to secure said journal pins in their respective positions.

4. A parallel rule according to claim 2 having each roller bored axially with a ball race groove formed intermediate the ends of the bore, a pair of cylindrical blocks mounted in each said bore from each end having the inner ends shaped to provide a ball race groove complementary to that in the roller, ball bearings in said grooves, an axle mounted in the walls of each slot supporting each said roller and screws to hold said cylindrical blocks in position.

5. A parallel rule according to claim 2 each roller having a bore, and counterbores axially and forming seats in the outer ends, an annular disc mounted in each end of the bore in engagement with one of said respective seats and an axle mounted in the walls of each slot supporting each said roller.

References Cited in the tile of this patent UNITED STATES PATENTS 287,200 Wachs Oct. 23, 1883 1,333,216 Pajeau Mar. 9, 1920 1,368,465 Sutliffe Feb. 15, 1921 1,602,276 Lutz Oct. 5, 1926 1,887,436 Schacht Nov. 8, 1932 2,506,243 Sill May 2, 1950 2,670,541 Priess Mar. 2, 1954 2,800,720 Kristiansen July 30, 1957 FOREIGN PATENTS 642,348 Great Britain Aug. 30, 1950 822,660 Germany Nov. 26, 1951 

